Corps set to reduce flows from Savannah River dams this fall

Thomas Saxon and Ashley Smith swim in Hartwell Lake at Darwin Wright Park after a break in the rain late Tuesday afternoon.

Anderson Independent Mail

HARTWELL - The U.S. Army Corps of Engineers has completed an environmental assessment of the Savannah River Basin that all but guarantees less water will be released from Hartwell Dam this winter — assuming the lake doesn't recover more than four feet in the meantime.

With the new assessment and an implementation plan weeks away from completion, drought conditions will trigger stricter reductions starting in November.

Hartwell Lake has been at the corps' Drought Level 2 for more than a year.

As of late Monday, Hartwell Lake stood at 649.81 feet above sea level — half a foot better than the three-year low Hartwell hit 10 days ago but still 11 feet below full pool.

Col. Jeff Hall, commander of the corps' Savannah District, approved and signed a "Finding of No Significant Impact" document on July 30 after 10 months of research and collaboration with state and federal natural resource agencies.

In addition to monitoring lake levels at Hartwell and Thurmond lakes, the corps will use the stream flow of a major Thurmond Lake tributary as the gauge of a drought's severity.

In a prepared statement, Hall said the corps' assessment gave operators the information they need to reduce flows based on average inflows from the Broad River during the year while in different drought levels and set lower wintertime outflows.

"These actions will allow us to improve water storage for the current and future droughts," Hall said.

The corps last changed its drought response plans in 2006, before the region's drought of record drained Hartwell Lake to a historically low 637.53 feet above sea level on Dec. 9, 2008.

Hartwell, completed 50 years ago, is full at 660 feet above sea level and stood at 649.82 feet on Monday morning — up more than half a foot with rainfall over the past 10 days.

The lowest the lake has stood over the past three years is 649.26 feet, a level it hit on Aug. 3.

Drought Level 3 is triggered at 646 feet — a mark that the corps predicts the reservoir will hit some time in October.

The new assessment will change wintertime releases from the corps' reservoir system during drought levels 2 and 3.

Under the plan, outflows from the Thurmond Dam will be reduced to 3,600 cubic feet per second from Nov. 1 through Jan. 31 while in Drought Level 2.

It will go down to 3,100 cubic feet per second from Nov. 1 through Jan. 31 if the reservoir enters Drought Level 3.

Hartwell Lake would, in turn, not need to release as much water, as the reservoirs work in tandem.

The corps lakes have been at Drought Level 2 for nearly a year.

Under the current drought plan, outflows at Drought Level 2 are set at 4,000 cubic feet per second year round.

Col. Hall used his discretion in October 2011, to further reduce outflows to 3,800 cubic feet per second when engineers and long-range forecasters realized how dry 2012 promised to be. That was the most he could reduce outflows without the assessment completed this summer.

Anyone with an interest in the lake, including multiple environmental agencies, had a chance to comment on the assessment before Hall signed the Finding of No Significant Impact.

Everything from dissolved oxygen content in the Savannah Harbor to drinking water in Augusta and river habitat for the shortnosed sturgeon and other endangered species up and down the basin had to be weighed before the corps could give the green light to reducing flows from the reservoirs.

A separate comprehensive study of the basin will get under way this fall with input from the corps, environmental agencies from Georgia and South Carolina and experts with The Nature Conservacny, said Ken Rentiers, the deputy director for land, water and conservation for the South Carolina Department of Natural Resources.

No timetable has yet been set for when the comprehensive study might be complete.

This study will recommend how to manage the Savannah River during times of drought, Rentiers said, and — once complete — will supercede the drought response plan the corps announced Monday..

Meanwhile, the corps' seasonal flow reduction could if needed be extended through the month of February with approval from the National Oceanic and Atmospheric Administration National Marine Fisheries.

The Broad River's stream flow will be considered using the U.S. Geological Survey gauge near Bell, Ga. Because the Broad River is a large, unregulated tributary that flows into the Thurmond reservoir, it provides an accurate representation of natural inflow to the Savannah River Basin.

If stream flows at the Broad River gauge are less than or equal to 10 percent of the historical flow rate over a 28-day average, the corps will reduce outflows to 4,000 cubic feet per second in Level 1 and 3,800 cubic feet per second in Level 2.

For more information, visit http://www.sas.usace.army.mil/reports.html.